Gas leak valve device



M. E. MOI

April 3o, 1968 GAS LEAK VALVE DEVICE 2 Sheets-Sheet l Filed Sept. 27, 1965 mwN f T WM mi. m n d @u s m NN @N QN w .w RN RN @N www www NS WS* www www/g 915K Ma/wey April 30, 1968 M. E. Mol 3,380,473

@As LEAK VALVE DEVICE Filed Sept. 27, 1965 2 Sheets-Sheet min/ffm? 645 Pifssdff :iA/:W5 fLE/f/i/V 108 132 7 J M6 4W 134 OUT/0 1354* Yncm/ ma;

far-aeg United States Patent O 3,380,473 GAS LEAK VALVE DEVICE Manfred E. Moi, Princeton, NJ., assigner to Radio `Corporation of America, a corporation of Delaware Filed Sept. 27, 1965, Ser. No. 490,341 16 Claims. (Cl. 137-4875) This invention relates to an improved gas leak valve device for selectively permitting gas to be introduced from a gas reservoir first enclosure into a second enclosure and, more particularly, to such a device which is capable of automatically maintaining the gas pressure in the second enclosure -at a preselected value within an extremely wide pressure range.

In accordance with the present invention, a movable valving element composed of a relatively soft material, such as copper, in the form of a cone cooperates with a valve seat member composed of a relatively hard material, such as stainless steel. More particularly, the valve seat member has a -hole therethrough, the hole having a diameter which is intermediate the smallest .and the largest diameter of the copper cone, so that the copper cone partially fits into the hole in the valve seat member. The edge of the hole of the valve seat member facing the copper cone is made sharp so as to be capable of biting into the copper cone to form a breakable gas seal. The copper cone is located within the second enclosure and is supportedby one end of a stiff longitudinal resistive member, the other end of which is secured to the first enclosure. This longitudinal member is composed of a material, such as Nichrome or stainless steel, which has a relatively large temperature coefficient of expansion. The length of this longitudinal member 'at a first temperature is such that the copper cone is maintained in tight engagement with the sharp edge of the valve seat member to form a breakable gas seal and at a second temperature is such that the copper cone is maintained in spaced relationship with respect to the valve seat member to permit gas to leak into the second enclosure from the first enclosure at a rate dependent on the amount of spacing. The amount of spacing and therefore the rate of the gas leak depends upon the v-alue of the second temperature. The gas pressure in the second enclosure can be maintained at a preselected value by utilizing a pressure sensing element within the second enclosure to control the root mean square value of heating current applied to the longitudinal member.

The gas leak valve device of the present invention is capable of operating at any pressure within a pressure range extending from -10 millimeters of mercury to several'A atmospheres. Another feature of the gas leak valve of the present invention is that it may be automatically and remotely operated, so that it can be used inside of bell jars and other enclosures.

The gas leak valve of the present invention is well suited for direct attachment to commercial gas bottles. However, it finds particular use in systems requiring minute quantities of pure gas at a predetermined relatively low pressure. For instance, the present invention has been found to be particularly useful in maintaining the gas pressure within a gas laser discharge tube, despite the tendency of an operating gas laser to lose gas pressure by so-called clean-up of a certain amount of the gas therewithin over a long period of time. Thus, when the gas leak valve `device of the present invention is used with a gas laser, expensive rebuilding and refilling of old laser tubes is avoided.

It is therefore an object of the present invention to provide an improved gas leak valve device.

It is a more particular object of the present invention to provide a gas leak valve device which is simple, rugged,

reliable, of low cost, and which does not strain vacuum systems.

These and other objects, features and advantages of the present invention will become more apparent from the following detailed description taken together with the accompanying drawings, in which:

FIG. 1 is a block diagram of a preferred embodiment of the present invention in combination with a gas laser discharge tube.

FIGS. 2A and 2B show in detail the configuration of the movable valving element of the gas leak valve shown in FIG. 1.

FIG. 3 is a first preferred embodiment of the controlled heat current source shown in FIG. l, which is most useful over a pressure range extending from 10-5 millimeters of mercury to 760 millimeters of mercury; and

FIG. 4 is a second preferred embodiment of the controlled heat current source shown in FIG. l, which is most useful at low pressures extending down to the order of 10'I millimeters of mercury.

Referring now to FIG. l, there is shown a gas-reservoir first enclosure and a second enclosure 102. Second enclosure 102 is made up of a gas laser discharge tube portion 104 which is coupled by coupling portion 112 to first tubule portion 106, containing gas pressure sensing element 108, and to a second tubule portion 110, connected to first enclosure 100. As shown, all of the walls of second enclosure 102, except for the small region at the end of second tubule portion connected to first enclosure 100, are composed of glass. Second enclosure 102 is initially evacuated by means not shown and then sealed.

First enclosure 100 includes a first metallic tubular portion 112, preferably composed of Kovar, interconnected end to end, as shown, to a similar second metallic tubular portion 114 by means of a ceramic ring 116.

Interconnecting the end of the second tubule portion 110 of second enclosure 102 to the left end of first tubular portion 112 of first enclosure 100 is valve seat member 118. Valve seat member 118, which is composed of a relatively hard material, such as stainless steel, has va hole of predetermined diameter extending therethrough. The boundary between the face of valve seat member 118 adjacent second enclosure 102 and the end of hole 120 which is proximate to second enclosure 102 is made to form a sharp edge 122.

Moving valving element 124, which is composed of a relatively soft material, such as copper, has the shape shown in detail in FIGS. 2A and 2B. More particularly, as shown in FIG. 2A, movable valving element 124 includes first cylindrical portion 200 having a diameter which is just slightly smaller than the predetermined diameter of hole 120 in valve seat member 118. Movable valving element 124 further includes a conical-shaped portion 202 having a maximum diameter which is greater than the predetermined diameter of hole 120 in valve seat member 118 and a minimum diameter which is smaller than the predetermined diameter of hole 120 in valve seat member 118. Conical-shaped portion 202 of movable valving element 124 is coupled to first cylindrical portion 200 thereof by coupling portion 204, as shown. A second cylindrical portion 206 of movable valving element 124 extends from the maximum diameter end of conical-shaped portion 202. As shown in detail in FIG. 2B, first cylindrical portion 200 of movable valving element 124 has four slots 208 parallel to the axis thereof which are equally spaced about the circumference thereof. Further, rst cylindrical portion 200 of movable valving element 124 includes a centrally located hole 210 therethrough.

Returning to FIG. l, movable valving element 124 is disposed with first cylindrical portion 200 thereof in sliding engagement with hole 120 of valve seat member 118 and with second cylindrical portion 206 thereof within second enclosure 102. Therefore, conical-shaped portion 202 of movable valving element 124 is so positioned as to be able to engage sharp edge 122 of valve seat member 118. The end of second cylindrical portion 206 of movable valving element 124 is fieXibly connected to valve seat member 118 by means of nickel ribbon 126.

Centrally located within first enclosure 100 is a stiff longitudinal resistive member 128 which is composed of a Nichrome or stainless steel rod. Both Nichrome and stainless steel have a relatively high temperature coefficient of expansion. The left end of longitudinal resistive member 128 is fastened through hole 210 to first cylindrical portion 200 of movable valving element 124, thereby providing support for movable valving element 124. The right end of longitudinal resistive member 128 is secured to second tubular portion 114 of first enclosure 100 by means of adjustable nut assembly 130.

Gas pressure sensing element 108, located in first tubule portion 106 of second enclosure 102, produces an electrical output signal which is a predetermined function of the gas pressure within second enclosure 102. The output signal from gas pressure sensing element 108 is applied over conductors 132 and 134 as an input to controlled heating current source 136, which selectively produces an output current controlled in accordance with the output signal obtained from gas pressure sensing element 108. An output series circuit from controlled heating current source 136 extends from output conductor 138 of controlled heating current source 136 through metallic first tubular portion 112 of first enclosure 100, valve seat member 118, nickel ribbon 126, movable valving element 124, longitudinal resistive member 128, adjacent nut assembly 130 and metallic second tubular portion 114 of first enclosure 102 to output conductor 140 of controlled heating current source 136. This results in longitudinal resistance member 128 being heated in accordance with the root mean square magnitude of the heating current applied therethrough from controlled heating current source 136.

Gas pressure sensing element 108 and controlled heating current source 136 may be of many types. For instance, an ionization gauge may be utilized at very low pressures down to l*10 millimeters of mercury. However the gas pressure sensing element and controlled heating current source of the type shown in FIG. 3 are particularly well suited for controlling the value of gas pressure over the extremely wide range from -5 millimeters of mercury to several atmospheres, while the gas pressure sensing element and controlled heating current source of the type shown in FIG. 4 are particularly well suited for controlling the value of gas pressure in the low range of gas pressures extending down to the order of 10-7 millimeters of mercury.

Referring now to FIG. 3, the gas pressure sensing element 108 comprises a thermistor 300, which has a large negative temperature coefficient of resistance. Controlled heating current source 136 comprises an auto-transformer 302 to which an A.C. voltage is applied. The output of auto-transformer 302 is applied to the input winding of stepdown transformer 304 through PNPN switch 306. The output winding of stepdown transformer 304 is applied to output conductors 138 and 140 of controlled heating current source 136 through ammeter 308. The output from auto-transformer 302 is also applied through output conductor 132 of thermistor 300 of gas pressure sensing element 108, output conductor 134 of gas pressure sensing element 108, and adjustable resistance 310, which may be a helipot, to the control electrode of PNPN switch 306 Referring now to FIG. 4, the gas pressure sensing element 108 comprises a Pirani gauge filament 400. Controlled heating current source 136 comprises a Wheatstone bridge made up of resistance 402, resistance 404, adjustable resistance 406 and Pirani gauge filament 400, which is connected thereto by conductors 132 and 134. The junction of resistance 404 and adjustable resistance 406 is connected to a point of reference potential through resistance 408. A first adjustable D.C. voltage source 410 has one terminal thereof connected to the point of reference potential and the other terminal thereof connected to the junction of resistance 402 and resistance 404. The junction of resistance 402 and conductor 134 is connected to the base of transistor 412. The emitter of transistor 412 is connected to the point of reference potential. Second adjustable D.C. voltage source 414 has one terminal thereof connected to the collector of transistor 412 and the other terminal thereof is connected to output conductor 140 of controlled heating current source 136. Output conductor 138 of controlled heating current source 136 is connected directly to the point of reference potential.

Considering now the operation of the gas leak valve device shown in FIG. 1, the length of longitudinal resistive member 128 at a first predetermined temperature thereof is set by means of adjustable nut assembly 130 to cause the conical-shaped portion 202 of movable valving element 124 to tightly engage the sharp edge of a valve seat member 118. Thus, at a temperature equal to or lower than this first predetermined temperature, movable valving element 124 in cooperation with valve seat member 118 forms a breakable gas seal.

Controlled heating current source 136 is adjusted to maintain longitudinal resistive member 128 at this first predetermined temperature in response to gas pressure sensing element 108 sensing a given desired gas pressure within second enclosure 102. However, second enclosure 102 is initially evacuated, or at least initially has a gas pressure therein which is substantially lower than the given desired gas pressure. Controlled heating current source 136, in response to gas pressure sensing element 108 sensing a gas pressure within second enclosure 102 which is substantially lower than the given Vdesired gas pressure, applies a relatively high heating current to longitudinal resistive member 128, causing the expansion thereof and resulting in movable valving element 124 being positioned in spaced relationship with respect to valve seat member 118. This permits gas from the gas reservoir contained Within first enclosure to enter second enclosure 102 through slots 208 in first cylindrical portion 200 of movable valving element 124 and the space which now exists between conical-shaped portion 202 of movable valving element 124 and valve seat member 118. Therefore, the gas pressure within second enclosure 102 increases. Gas pressure sensing element 108, in response to this increase in gas pressure within second enclosure 102, causes controlled heating current source 106 to reduce the root mean square magnitude of the heating current applied to longitudinal resistive member 128, thereby causing longitudinal resistive member 128 to contract and the spacing between conical-shaped portion 202 of movable valving element 124 and valve seat member 118 to be reduced. Due to this smaller spacing, the rate of flow of gas from first enclosure 100 to second enclosure 102 decreases.

It should be noted here that, due to the conical shape of portion 202 of movable valving element 124, the size of the area of the space between movable element 124 and valve seat member 118 varies more than linearly with respect to the variation in the length of longitudinal resistive member 128. Therefore, as gas pressure within second enclosure 102 approaches the given desired gas pressure, the rate of gas fiow from first enclosure 100 to second enclosure 102 s markedly reduced until the gas pressure within enclosure 102 finally equals the given desired gas pressure at which time conical-shaped portion 202 of movable valve element 124 comes into contact with and tightly engages valve seat member 118 to thereby seal second enclosure 102 from first enclosure 100. The fact that the rate of gas fiow from first enclosure 100 to second enclosure 102 varies at more than a linear rate with respect to longitudinal resistive member 128 makes it possi- -ble to introduce a relatively large amount of gas into second enclosure 102 from first enclosure 100 in a relatively short time, but yet provides extreme sensitivity in the introduction of a minute amount of gas from first enclosure 100 to second enclosure 102 when the difference between the gas pressure within second enclosure 102 and the -given desired gas pressure is very small.

Whencontrolled heating current source 136 takes the form shown in FIG. 3, PNPN switch 306 will be closed, if at all, for only a portion of each cycle of the applied alternating current voltage. The size of this portion depends upon the setting of auto-transformer 302 and variable resistance 310. More particularly, PNPN switch 306 "will close only in response to the potential difference between the control electrode thereof connected to the variable tap of auto-transformer 302 having a given polarity and a given magnitude. Once closed, PNPN switch 306 will open only in response to this potential difference having an opposite polarity from this given polarity. It will be seen that this potential difference depends upon the setting of auto-transformer 302, the setting of variable resistance 310 and the resistance of thermistor 300. The resistance of thermistor 300 depends upon its temperature which, in turn, depends upon the gas pressure within second enclosure 102. The heating current applied to conductors 138 and 140 will have a root mean square value which depends upon the setting of auto-transformer 302 and the size of the portion of each cycle of alternating current voltage during which PNPN switch is closed. Therefore, auto-transformer 302 and variable resistance 310 may be set in accordance with the given desired gas pressure within second enclosure 102.

When controlled heating current source 136 takes the form shown in FIG. 4, the temperature of Pirani gauge filament 400 is a function of both the current therethrough and the gas pressure within second enclosure 102. The current through Pirani gauge filament 400 depends upon the setting of first D.C. voltage source 410 and the setting of adjustable resistance 406 of the Wheatstone bridge. Voltage source 410 and adjustable resistance 406 of the Wheatstone bridge are set so that the Wheatstone bridge will be balanced when the gas pressure within second enclosure 102 is equal to the given desired gas pressure. Transistor 412 acts as a D.C. amplifier for controlling the value of the heating current applied to conductors 138 and 140 in accordance with the signal applied to the base of transistor 412 and the setting of second adjustable voltage source 414. When the gas pressure in second enclosure 102 is equal to the given desired gas pressure and the Wheatstone bridge is balanced, transistor 412 permits heating current to be applied to longitudinal resistive member 128, shown in FIG. l, of a value just sufficient to maintain the temperature of longitudinal resistive member 128 at the aforesaid first predetermined temperature, so as to maintain the gas leak valve closed. However, when the gas pressure within gas enclosure 102 is lower than the desired given pressure, the Wheatstone bridge will be unbalanced by an amount which is a direct function of the difference between the gas pressure within second enclosure 102 and the desired given pressure. Transistor 412, acting as a D.C. amplifier, will then provide a greater heating current to longitudinal resistive member 128 over conductors 138 and 140, which heating current has a value which is a direct function of the degree of unbalance in the Wheatstone bridge.

Although only certain embodiments of the present invention have been described herein in detail, it is not intended that the invention be restricted thereto, but that it be limited only by the true spirit and scope of the appended claims.

What is claimed is:

1. A gas leak valve device for selectively permitting gas to be introduced from a gas-reservoir first enclosure into a second enclosure, said device comprising a valve incl-uding a valve seat member composed of a relatively hard material which is located at the junction between said first and second enclosures, said valve seat member having a hole of predetermined shape and predetermined size extending therethrough interconnecting said first and second enclosures, wherein the boundary between the face of said valve seat member adjacent said second enclosure and that end of said hole therethrough which is proximate to said second enclosure forms a sharp edge, a movable valving element composed of a relatively soft material, said valving element including a conical-surfaced portion the cross section of which has said predetermined shape and varies from a first given size smaller than said predetermined size to a second given size larger than said predetermined size, said valving element being disposed in said second enclosure with said conical-shaped portion thereof oriented to fit into said hole of said valve seat member and engage the sharp edge thereof, and a stiff longitudinal resistive member in said first enclosure having one end thereof secured to said first enclosure and the other end thereof attached to said valving element, said longitudinal resistive member being composed of a material having a substantial coefficient of thermal expansion, the length of said longitudinal resistive member at a first given temperature thereof being such as to maintain said conical-shaped portion of said valving element in tight engagement with the sharp edge of said valve seat member, whereby said sharp edge of said relatively hard valve seat member bites into said relatively soft valving element to form a fbreakable gas seal, the length of said longitudinal resistive member at a second given temperature thereof being such as to maintain said valving element in spaced relationship with respect to said valve seat member to permit gas to leak into said second enclosure from said first enclosure at a rate dependent on the amount of said spacing, the amount of said spacing depending upon the value of said second given temperature, and said device further including electrical means for applying a controlled heating current through said longitudinal resistive member to control the temperature thereof in accordance with the root mean square magnitude of the current therethrough.

2. The device defined in claim 1, wherein said valve seat member is composed of stainless steel and said valving element is composed of copper.

3. The device defined in claim 1, wherein said longitudinal resistive member is composed of Nichrome.

4. The device defined in claim 1, wherein said longitudinal resistive member is composed of stainless steel.

5. The device defined in claim 1, wherein said predetermined shape of said hole of said valve seat member and said conical-shaped portion of said valving element is circular, said hole having a predetermined diameter.

6. The device defined in claim 5, wherein said valve element further includes a circular cylindrical portion having a diameter which is slightly less than said predetermined diameter, said circular cylindrical portion being disposed within said hole of said valve seat member in sliding engagement therewith, and an additional portion attaching said circular cylindrical portion to said conioalshaped portion, said cylindrical portion having a plurality of circumferentially spaced slots about the periphery thereof for permitting gas from said first enclosure to ow therethrough.

7. The device detined in claim 1, wherein said first enclosure includes separate first and second electrically conducting longitudinal portions disposed end to end, insulating means coupling the adjacent ends of said first and second longitudinal portions, and valve seat member being attached to the other end of said first longitudinal portion of Said first enclosure, flexible electrically conducting means connecting said valve element to said other end of s-aid first enclosure, said valve element being electrically conducting, electrically conducting means securing said one end of said longitudinal resistive member to the other end of said second longitudinal portion of said first enclosure, and wherein said electrical means includes first and second output voltage terminals, said first terminal being connected to s-aid first longitudinal portion of said first enclosure and said second terminal being connected to said second longitudinal portion of said first enclosure, whereby there is provided an electrical circuit including said longitudinal resistive member for applying heating current therethrough.

8. The valve defined in claim 7, wherein said first and second longitudinal portions of said first enclosure are each composed of Kovar tubes and said insulating means comprises a ceramic ring.

9. The valve defined in claim 7, wherein said fiexible electrically conducting means comprises a nickel ribbon.

10. The device defined in claim 7, wherein said valve seat member is electrically conducting and said flexible electrically conducting means is connected to the other end of said first longitudinal portion 0f said Vfirst enclosure through said valve seat member.

11. The device defined in claim 1, wherein said one end of said longitudinal resistive member is secured to said first enclosure through a threaded nut, whereby the effective length of said longitudinal resistive member at any given temperature Imay be set.

12. The device defined in claim 1, wherein said electrical means includes a sensing element located within said second enclosure having a value of resistance which is a predetermined function of the gas pressure within said second enclosure, and control means responsive to said value of resistance of said sensing element for controlling the root mean square magnitude of heating current applied to said longitudinal resistive member.

13. The device defined in claim 12, wherein said sensing element comprises a thermistor, and wherein said control means comprises a source of A.C. voltage, coupling means for applying heating current to said longitudinal resistive member in response to the energization thereof, means including a signal-controlled switch having a control electrode for energizing said coupling means with said A.C. voltage in response to the closure of said switch, and .an adjustable resistance connected in series with said thermistor `between a point of A.C. potential and said control electrode of said switch for effecting the closure of said switch in response to the resist-ance of said thermistor falling below a given value which depends on the setting of said adjustable resistance and the pressure of said gas in said second enclosure.

14. The device defined in claim 13, further including means for adjusting the amplitude of said A.C. voltage.

15. The device defind in claim 13, wherein said switch is a PNPN semiconductor switch, wherein said coupling means comprises a transformer, and wherein said adjustable resistance comprises a helipot.

16. The device defined in claim 12, wherein said sensing element comprises a Pirani gauge filament, and wherein said control means comprises a Wheatstone bridge including said Pirani gauge filament as one arm thereof and means for setting the value of resistance of said Pirani gauge filament at which said bridge is balanced to thereby produce an error signal from said Wheatstone bridge when it is not balanced, and means responsive to the magnitude and polarity of said error Signal for controlling the magnitude of heating current applied to said longitudinal resistive member of said valve to maintain the gas pressure in said second enclosure at a predetermined value which depends on the value of resistance of said Pirani gauge filament lat which said bridge is balanced.

No references cited.

M. CARY NELSON, Primary Examiner.

R. J. MILLER, Assistant Examiner. 

1. A GAS LEAK VALVE DEVICE FOR SELECTIVELY PERMITTING GAS TO BE INTRODUCED FROM A GAS-RESERVOIR FIRST ENCLOSURE INTO A SECOND ENCLOSURE, SAID DEVICE COMPRISING A VALVE INCLUDING A VALVE SEAT MEMBER COMPOSED OF A RELATIVELY HARD MATERIAL WHICH IS LOCATED AT THE JUNCTION BETWEEN SAID FIRST AND SECOND ENCLOSURES, SAID VALVE SEAT MEMBER HAVING A HOLE OF PREDETERMINED SHAPE AND PREDETERMINED SIZE EXTENDING THERETHROUGH INTERCONNECTING SAID FIRST AND SECOND ENCLOSURES, WHEREIN THE BOUNDARY BETWEEN THE FACE OF SAID VALVE SEAT MEMBER ADJACENT SAID SECOND ENCLOSURE AND THAT END OF SAID HOLE THERETHROUGH WHICH IS PROXIMATE TO SAID SECOND ENCLOSURE FORMS A SHARP EDGE, A MOVABLE VALVING ELEMENT COMPOSED OF A RELATIVELY SOFT MATERIAL, SAID VALVING ELEMENT INCLUDING A CONICAL-SURFACED PORTION THE CROSS SECTION OF WHICH HAS SAID PREDETERMINED SHAPE AND VARIES FROM A FIRST GIVEN SIZE SMALLER THAN SAID PREDETERMINED SIZE TO A SECOND GIVEN SIZE LARGER THAN SAID PREDETERMINED SIZE, SAID VALVING ELEMENT BEING DISPOSED IN SAID SECOND ENCLOSURE WITH SAID CONICAL-SHAPED PORTION THEREOF ORIENTED TO FIT INTO SAID HOLE OF SAID VALVE SEAT MEMBER AND ENGAGE THE SHARP EDGE THEREOF, AND A STIFF LONGITUDINAL RESISTIVE MEMBER IN SAID FIRST ENCLOSURE HAVING ONE END THEREOF SECURED TO SAID FIRST ENCLOSURE AND THE OTHER END THEREOF ATTACHED TO SAID VALVING ELEMENT, SAID LONGITUDINAL RESISTIVE MEMBER BEING COMPOSED OF A MATERIAL HAVING A SUBSTANTIAL COEFFICIENT OF THERMAL EXPANSION, THE LENGTH OF SAID LONGITUDINAL RESISTIVE MEMBER AT A FIRST GIVEN TEMPERATURE 